As level meter for fuel tanks, float elements are known, communicating the altitude of the float element via a potentiometer. To this end, the float element is connected to a contact pin contacting tracks of a potentiometer as a slide. Moving the contact pin or slide relative to the tracks functioning as position sensors results in a change of resistance. Depending on the change of resistance, the level can be determined by means of an appropriate evaluating means. Particularly with modern fuels and fuel mixtures, such level meters suffer from the disadvantage that the slide contacts may become conglutinated and/or the tracks are provided with a solid coating. Thereby, considerable measuring faults can be provoked. Further, using a slide contact is disadvantageous in that the slide contact as well as the tracks are subject to wear.
Furthermore, capacitive level meters based on a basically different principle are known as level meters. Such level meters do not have a float element. A printed circuit board is rather inserted into the fuel tank and the level is detected by a change of the dielectric constant of the medium between the two plates of the capacitor. Since the change of capacity of the capacitors depends on the level, the level can be detected from the change of capacity. Such level meters, however, are utterly complicated and expensive.